ex- boyfriend ? is this fate?

I recently followed my ex on social media. As soon as he saw it he instantly messaged me asking why did I follow him. I told him it was no big deal and he told me to call him. I ended up not calling him because I didn't want to really talk to him. A few days later he asked me again and I finally agreed to call him. We ended up having a good convo just like old times. Then 1 night he called to hang out I ended up hanging out with him. So far we've hung out 2 days straight. Its crazy because when we hang out he treats me like were just friends and hasn't tried anything yet which is fine with me.  The only thing i dont get is why doesn't he want to hang with me after all the bad things we went through? Its crazy because we always go through this thing where we would fall off and then some months later we're back cool again. What does this mean? Im a libra and hes a sagittarius by the way.